This project is devoted to the investigation of the functioning of lysosomes. Through study of the lysosomal, cytosolic, and Golgi alpha-D-mannosidases, we hope to uncover interrelationships among enzymes of the three cell compartments as well as unique roles of these enzymes. Extensive substrate specificity studies are planned. Experiments with an Acanthamoeba system which we have found allows phagolysome fusion to occur in vitro, will hopefully permit the identification of membrane and environmental factors which determine the specificity of the fusion among these vacuoles. The information obtained should contribute to our understanding of the intracellular dynamics of the lysosomal system.